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INTERNSHIP PROGRAM

USMAN INSTITUTE OF TECHNOLOGY

Department of Electrical Engineering Specialization in Electronics

PAKISTAN STEEL MILLS KARACHI

INTERNSHIP REPORT

Duration: Six Weeks August- 2014

Submitted To: Incharge (Trg. Wing) HRD

Submitted By: Nizam Uddin (270)

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PREFACE

I am highly indebted by this opportunity of working at one of the basic industry of our country. Working at Pakistan

steel was an unforgettable experience for me. The experience not only enhanced my knowledge, but it also gave

me first hand experience of how I will be rolling in my professional life.

This internship opportunity benefited me in diverse areas; the basic purpose being the plant training in different

plants of Pakistan Steel, providing the necessary knowledge for carrying out various kinds of electrical maintenance

and repair work.

I am extremely grateful for this experience for working in the departments I was assigned. These six weeks of

internship training not only trained me enough for the field work, but this also helped me in developing national

cohesion and solidarity. The moments spend at Pakistan Steel will be remembered as a cherished memory forever.

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ACKNOWLEDGEMENT

I am very thankful from the core of my heart to the honorable Chief Executive Officer, Pakistan Steel, for providing

me the opportunity for training and who’s intelligent, wise and sound leadership has converted man power into

winning combination by this industry into a Goldmine.

I wish to express my deep gratefulness to Mr. Wasif Mehmood, PEO (HRD) for his consideration and supervision. It

was a memorable time in Pakistan Steel due to his kind concern.

I am also thankful to MR Raza Muhammad Tunio, Incharge (HRD) and MR Yousuf Ayub, Dy. Manager/ Incharge (In

Plant Training) for his precious advice and for the great encouragement and cooperation because of which I have

successfully completed my internship training at Pakistan Steel where I learnt a lot.

Internee

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TABLE OF CONTENTS

PAKISTAN STEEL MILL ............................................................................................................ 5

HISTORICAL BACKGROUND .................................................................................................... 5

POWER EQUIPMENT REPAIRING SHOP- ELECTRICAL (PERS-E) ................................................. 6

POWER DISTRIBUTION NETWORK (PDN) .............................................................................. 11

STEEL MAKING DEPARTMENT (SMD) .................................................................................... 15

THERMAL POWER PLANT AND TURBO BLOWER STATION (tpp-tbs) ....................................... 18

CONCLUSION ....................................................................................................................... 23

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PAKISTAN STEEL MILL

Pakistan Steel Mills, is a global competitive, multi-billion state-owned mega corporation and the producer of the

long rolled steel and heavy metal products and entities in the country. Headquartered in Karachi, Sindh of Pakistan,

and the PSM is the current largest industrial mega corporation undertaking having a production capacity of 1.1—5.0

million tons of steel and iron foundries. Built with the contributions of the Soviet Union in the 1970s, it is the largest

industrial mega corporation complex, vastly expanded in an enormous dimensions construction inputs, involving

the use of 1.29Mn cubic meters of concrete; 5.70Mn cubic meters of earth work; and contains ~330,000 tones of

heavy machinery, steel structures and electrical equipments.

Pakistan Steel is spread over an area of 18,660 acres (about 29 square miles) including 10,390 acres for the main

plant, 8070 acres for township and 200 acres for 110 MG water reservoir. In addition, it has leasehold rights over an

area of 7520 acres for the quarries of limestone and dolomite in Makli and Jhimpir areas of district Thatta.

HISTORICAL BACKGROUND

In 1968 Government of Pakistan decided that the Karachi Steel Project should be sponsored in the public sector, for

which a separate Corporation, under the Companies Act, be formed. In pursuance of this decision, Pakistan Steel

Mills Corporation Limited was incorporated as a private limited company to establish and run steel Mills at Karachi.

Pakistan Steel Mills Corporation concluded an agreement with V/o Tyaz prom export of the USSR in January, 1969

for the preparation of feasibility report for the establishment of a coastal based integrated steel mill at Karachi. In

January 1971 Pakistan and the USSR signed an agreement under which the later agreed to provide techno-financial

assistance for the construction of a coastal-based integrated Steel Mills at Karachi. The foundation stone of this

vital and gigantic project was laid on 30th December, 1973 by the then Prime Minister of Pakistan. The mammoth

construction and erection work of an integrated Steel Mills, never experienced before in the country, was carried

out by a consortium of Pakistani construction companies under the overall supervision of Soviet Experts. Pakistan

Steel did not only have to construct the main production units, but a host of infrastructure facilities involving

unprecedented volumes of work and expertise. Component units of the Steel Mills numbering over twenty and

each a big enough factory in its own right were commissioned as they were completed between 1981 to 1985 with

Coke Oven and by-Product Plant coming on stream the first and the Galvanizing Unit the last. Commissioning of

Blast Furnace No.1 on 14th August, 1981 marked the Pakistan's entry into the elite club of iron and steel producing

nations. The project was completed at a capital cost of Rs.24, 700 million. The completion of the Steel Mills was

formally launched by the then President of Pakistan on 15th January, 1985. PAKISTAN STEEL today is the country's

largest industrial under-taking having production capacity of 1.1 million tons of steel.

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POWER EQUIPMENT REPAIRING SHOP- ELECTRICAL (PERS-E)

“To ensure running of electrical equipment of Pakistan Steel by provision of quality services in accordance with

standard norms, Power equipment repair shop is committed towards continuous improvement through

teamwork and participation”.

Different types, ratings and sizes of electric motors up to 500KW and transformers up to 1000KVA repairing are the

responsibility of this department. This department of steel mill performs following services:

1. Repair of electric motor

2. Rewinding

3. Repair of welding of power transformers

4. Repair of electromagnets

5. Repair of contacts and spares

6. Rewinding of coil and control transformers

For performing these services with ease this department is further divided into following sections:

1. Planning section

2. Assembly/ Disassembly section

3. Winding section

4. Transformers and electromagnetic repair section

5. Coil and spares section

6. Drying and impetration section

7. Testing section

PLANNING SECTION:

In this section the faulty machine is inspected and steps of repairing are

planned out. This section is the most important section, when the

defected machine is first brought in this section; an identification number

is assigned to the faulty machine before dispatching it for repairing.

The identification number contains:

its rating

a code representing the department of Steel Mills to which it

belong

the number of times this machine has been repaired

a code representing the fault

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ASSEMBLY/DISASSEMBLY SECTION:

After the inspection of fault machine is disassembled in this section and sent to the other sections for

repairing. After the required repairing has been done machine is again sent to this section for assembly.

WINDING SECTION:

In PERS-E, winding and rewinding section is divided into two parts:

AC and DC rewinding. The AC and DC motor rewinding section are

different because of the obvious difference in construction of the

two motors.

AC Winding:

There are two types of windings:

Chain winding-in which both coils are of same size

Concentric winding-in which coils are of different sizes

The following specifications of the windings are given to the

winders:

Pitch

Number of coil sets

No of coils

No of parallel paths

DC Winding:

There are two types of DC windings:

LAP WINDING:

This type of winding is used in DC generators designed for high-

current applications. The windings are connected to provide

several parallel paths for current in the armature. For this reason,

lap-wound armatures used in DC generators require several pairs

of poles and brushes. In lap winding, the finishing end of one coil is

connected to a commutator segment and to the starting end of

the adjacent coil situated under the same pole and so on, till all

the coils have been connected.

WAVE WINDING:

This type of winding is used in DC generators employed in high-

voltage applications. The two ends of each coil are connected to

commutator segments separated by the distance between poles.

This configuration allows the series addition of the voltages in all

the windings between brushes. This type of winding only requires

one pair of brushes. In practice, a practical generator may have

several pairs to improve commutation.

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Lap and wave winding can be simplex, duplex, triplex, etc. The adjectives simplex and multiplex refer to the

number of parallel paths between the brushes (winding terminals).

TESTING SECTION:

After all the repairing has been carried out, the machine is brought in the testing section to assure that the

machine is working perfectly before sending it to the concerned department. To check the reliability of the

machine following tests is performed in this section.

1. Appearance Test:

Firstly the appearance test of the machine is performed in which cover, terminal box and hooks are

checked, and also whether the leads are proper.

2. Continuity Test (Megger):

With megger the continuity of both primary and

secondary are tested. Then the continuity of primary

with the body and secondary with the body is checked.

Lastly, the continuity of primary to secondary with

each other is tested.

3. Regularity Test:

There are two voltage regulators:

o L.V Regulator (0-415V)

o H.V Regulator (0-11kV)

The regulator first tests the machine at low voltage for safety and later it is checked by the tongue tester

for balanced phase currents. If current is balanced, then after 10mins the voltage is increased till rated

value for further tests.

4. Current Imbalance Test:

An autotransformer is used to apply a very high three phase voltage to the windings. A compass is inserted in the machine and the stator windings are tested in this way to find out whether there is any sort of current imbalance created. The needle must rotate completely if there is no imbalance of currents.

5. No Load Test:

This test is performed to determine:

no-load current

no-load power factor

windage and friction losses

no-load core loss

no-load input

no-load resistance and reactance.

This test is performed with different values of applied voltage below and above rated voltage while the

motor is running at no-load.

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6. Insulation Test:

This test is to measure insulation resistance of each winding and of all auxiliary and supplementary

elements against earth.

7. High Voltage test:

In high voltage test a high voltage is given to the windings for 1 minute. If a spark is produced during this

period, it indicates the presence of fault. The voltage to be given for AC machines is calculated as:

For AC:

Rated voltage * 1.6 = high voltage to be given in the test

For DC:

Rated voltage * 1.7 = high voltage to be given in the test

8. Vibration Test:

At rated voltage and rpm machine is checked for vibrations using vibrometer. It is checked whether the

vibrations of the machine are within the permissible rating.

9. Sound Test:

Sound test is done to check the ball bearings in the machine. The machine is made to run at rated voltage

and rpm, one end of a metallic rod is touched to the body while the other end is put near the ear to hear

for the noise. If a hammering sound is heard it means that the bearing is faulty and might be broken.

TRANSFORMER SECTION:

Transformers up to 1000KVA are brought in this section for repairing..

Depending upon the nature of the faults, the tests performed on the

transformers are;

1. appearance test

2. turns ratio test,

3. open circuit test

4. short circuit test

5. high voltage test

6. winding test

7. insulation test

BALANCING SECTION:

In this section, the rotor is balanced. The machine has two moveable

arms on which the shaft is mounted. Its meter shows reading for both

the sides. If the meter shows a deflection the rotor is unbalanced. The

imbalance is compensated either by adding a weight (specially made

by lath machine) or by cutting small portions.

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FURNACE SECTION:

Furnace section is for removing humidity and moisture present in the

machine stator or rotor\ armature. Different parts of the machines

are dipped in varnishing tank for proper insulation.

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POWER DISTRIBUTION NETWORK (PDN)

PDN stands for Power Distribution Network. The Power Distribution Network of the Pakistan Steel Mills deals with HT that is 132 kV or 11 kV. The PDN manages the distribution of power generated by thermal power plant and that supplied by KESC. It has two lines:

TPP-the stable load of Steel Mills is connected to TPP MSDS-Main step down substation-the fluctuating load of Steel Mills is connected to MSDS. The fluctuating

load refers to HSM, CRM etc.

176 MW is the maximum demand of electric power by Pakistan Steel. This requirement is partially met by TPP-TBS, having the ideal generation capacity of 110 MW; however the actual capacity is 91MW. The remaining 85 MW fluctuating load of Rolling Mills is received from KESC through a 132 kV grid station by means of two 63 MVA transformer at main step down station (MSDS). Pakistan Steel is connected to the 132 kV KESC grid through two independent 132 kV circuits. One of the circuit is connected to the rolling mills through two 132 KV/11KV- 63 MVA transformer. The second circuit of 132 kV network is connected at TPP through two 132/11.5/6.9 KV-63 MVA transformers to synchronize all the three generators of Pakistan Steel with KESC to import or export the electrical energy according to requirement.

The installed capacity of generators is 110 MW. The PSM load is around 80-100 MW which is the stable load, the fluctuating load is about 30 MW. The motors when from no-load to full load cause a voltage dip along with high in-rush current, this results in fluctuations. The greater the rating of the motor, the greater is the time it takes to come up from that dip. Departments like sea water pump house, CRM-Cold Rolling Mills, Cook Oven Gas Department, blast furnace are connected to both MSDS and TPP due to their heavy unstable load.

MAIN STEP DOWN SUBSTATION (MSDS):

It has a three winding step down transformers connected to a 132 kV bus bar. Secondary voltage of 11kV is distributed to different departments to operate high rated motors. MSDS have a total of three transformers, two of which are in running condition while the third one is reserve.

Two lines of 132 kV from Pipri Grid Station are connected to two transformers (63MVA each) at MSDS. These HT lines before connecting to transformers are provided with safety system through isolator circuit breakers and lightning arrestors. MSDS has Remote Control Panel to control the switching of these circuit breakers.

PSO transformer oil of category 2 is used. PSO oil can bear 5000A and it is used at HT side of transformer. Buckholz relay located between main tank and conservator tank determines any fault in transformer. Syphon tanks are placed with transformer to filter out the sludge formed due to contamination of oil. We can define the symphonic flow as less dense evaporated steam flowing upward. Hence, sludge due to impurities of oil moves upward and is filtered out. These transformers step down 132 kV to 11 kV. And these 11kV lines are further distributed to different departments of PSM through underground cables. Oil immersed paper insulted cables and cross linked polyethylene cables (XLPE) are used for 11kV distribution to different DS and TS.

OPERATION SECTION:

This section has a huge panel which depicts the layout of the entire distribution network. There is a specific colour coding in the one line diagram. The green colour indicates 11kV, red 6.6kV and white shows the 132kV interconnection between Steel Mill and KESC. The panel has light indication system to show fault points and the maintenance work being carried out throughout the DSs. Coordination between the operating staff and the maintenance staff is based on Telemetry.

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Main function of this section is maintaining continuous power supply from Pipri Grid Station to MSDS and to all 23 DS and to the various equipment on round the clock basis. For this purpose, a team of engineers under the supervision of Shift In-charge are deputed at Power Dispatch Centre at OPCC Building. The operation staff performs following functions:

Switching at different DS during normal conditions and emergency caused by any breakdown and electrical faults.

Maintain hourly log books at DS to monitor the operation of the equipments.

Perform shift-wise inspection of equipments at the basement of DS and allied cable tunnels.

Operate street lights/area lights and attend minor faults during shifts.

Attend any problem in power supplying network.

The operation section also performs planning and scheduling of preventive maintenance and testing of following equipments:

HT bus bars,

HT circuit breakers,

Protection relays,

HT cables,

Calibration of energy meters,

Testing of safety items

Cleaning and up-keeping of DSs and OPPC building.

Maintenance of Lighting at DSs and OPPC Building.

MAINTENANCE SECTION:

The maintenance section headed by DOH/Manager Maintenance PDN has been divided into the following section:

Network Section

Repair Section

Mechanical Repair Section and Workshop

NETWORK SECTION:

The network section is responsible for cable maintenance, transmission line, and emergency units and street lights control. The main step down station (MSDS) step downs the voltage from 132KV to 11KV with the help of two 63MVA transformers, each transformer consists of two secondary windings of 11KV each.

The load profile of Steel Mill is as under:

Connected Load: 330MW

Full Load: 186MW

Average Load: 110MW

Fluctuating Load: 5-30MW

The circuit breakers used around the campus are mostly OCBs (oil circuit breakers), air circuit breakers and vacuum circuit breakers. For earth indication Peterson coil and for fault indication CTs are used.

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The task of distribution around Steel Mill is adequately performed by a 12km cable tunnel. The tunnel covers the entire area of Steel Mill. The length of HV cables is about 500,000m. Telecommunication lines are also present in the tunnel. The tunnel is provided with an efficient exhaust system and the various outlets.

The following works are being performed by Network Section:

Repair and maintenance of 132kV transmission lines,

Repair and maintenance of 63MVA transformers at MSDS,

High voltage cable testing,

Repair of high voltage cables,

Repair and maintenance area and street lights,

Repair and maintenance of cable tunnels with its ventilation system, and

Repair and maintenance of overhead lines at slag dump area and underground cable up to Sewerage Treatment Plant.

REPAIR SECTION:

The repair section is responsible for the repair and maintenance of various elements of different DSs such as cables, isolators, circuit breakers, bus bars, transformers, etc. Oil filled cables are those where the insulation is provided by oil. This is Russian technology. This task of filling the vertical cables with oil is also assigned to the repair section.

The following tasks are being performed:

Planned preventive maintenance of circuit breakers,

Planned preventive maintenance of bush bars,

Planned preventive maintenance of rectifiers and charger system at DSs,

Planned preventive maintenance of switchgear yard at MSDS,

Planned preventive maintenance of MG sets installed at 1 DS (Blast Furnace)

Planned preventive maintenance of panel mounted isolators

Capital repair of circuit breakers,

Planned preventive maintenance of cooling fans of 63 MVA transformers at MSDS, and transformers installed at different DSs, and

Planned preventive maintenance of exhaust fans, cooling fans and ventilation motors.

MECHANICAL SECTION AND WORKSHOP:

Mechanical Workshop provides all mechanical facilities and machining works required for maintenance of PDN equipments. Mechanical section carries out the following tasks:

Repair and Maintenance of cooling fans and ventilation system through the Main Plant.

Repair and maintenance of ventilation system at different DS.

Mechanical works of lighting towers and street lights poles

Repair works of cable tunnels

Mechanical repair of MSDS switch gear

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LOGISTIC AND TECHNICAL SECTION:

This section performs the following functions:

To maintain record of all drawings, manuals, instruction books of all the electrical equipments installed at the PDN Department,

To maintain layouts and plans of installation of equipments,

To maintain all test certificates, inspection certificates and record of equipments,

To prepare details and drawings of any technical modification required in the system,

To maintain energy consumption record ,energy balance sheet and billing records,

To organize technical training ,conduct examination and coordinate with in plant training department of HRD,

To initiate insurance claims and provide pre-requisite information for finalization of such planes,

To plan the annual material requirements, initiate purchase indents and arrange procurement of required maintenance material.

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STEEL MAKING DEPARTMENT (SMD)

Hot metal is transported from the two Blast Furnaces by rail

cars in 140 tones open transfer ladles and is charged into the

mixer by crane. The mixer acts as a buffer storage vessel to

accommodate variations between iron production and the

steel making shop operations. To maintain the temperature in

the mixer natural gas burners heat the surface of the hot

metal.

Hot metal is poured from the mixer into a charging ladle

mounted on a self-propelled rail car. During pouring the ladle

car is positioned on a weighbridge. A sample of hot metal is

taken for analysis as sit is poured and the temperature of the charge in the ladle is measured using an expandable

immersion thermocouple.

The hot metal is charged into the converter by crane. Likewise weighed quantities of steel scrap and pig iron are

charged from scrap boxes. The latter are prepared in the scrap pit located inside the SMD Building.

After charging, the converter is rotated to a vertical position and one of the two water-cooled oxygen lances is

lowered for blowing. The height of the lance nozzle relative to the liquid metal surface is important in order to

create the optimum creation conditions. To attain the desired carbon content in the refined steel and to oxidize

other impurities a calculated volume of oxygen is blown into the converter at a controlled flow rate. During blowing

process a pre-determined quantity of calcinated lime is added to the vessel to produce a slag which aids the

refining process. Flouride is added for slag fluidity control. Iron Ore is sometimes added for temperature control.

Coke can be added for carbon control.

The converter additives are stored in feed bins. Materials are weighed out as require and are transferred by

conveyer to a holding bin, From where they are discharged own a chute into the converter.

After blowing, the converter is tilted and the temperature of the steel is measured using an expandable immersion

thermocouple. A sample is taken for analysis at the express spectrographic laboratory within the SMD building. If

the desired steel temperature and carbon contents are not attained then a re below is undertaken. When the end-

point conditions are achieved, the converter is tilted and steel is poured into at 130 tonne steel ladle through a trap

hole. Alloying materials are added to the ladle during and ferrosilicon, are added to the ladle during tapping. Ladle

additives, namely ferromanganese and ferrosilicon, are weighed out of storage bins and loaded into boxes which

are transported by a fork after truck to the steel ladle side of the converter. Two boxes can be positioned together

on a discharging device and the contents added to the ladle. Aluminium bars and bags of coke breeze are added to

the ladle by hand. For certain steel specification calcium silicate is also added to the ladle.

On completion of tapping, the steel ladle is moved by a self-propelled rail car into the ladle bay of the casting area.

The converter is titled in the opposite direction and the slag is discharged into a slag pet., which is taken by a self-

propelled rail car to the slag bay.

During blowing, large quantities of waste gas are produced, mainly carbon monoxide and carbon dioxide. The

converters have an open gas extraction hood, which a lows excess air to be drawn in so that the carbon monoxide is

burnt. Energy is recovered from the hot waste gases by a steam-producing boiler. The boiler consists of panels of

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pipes, attached to the internal surfaces of the hood and Extraction ducts, through which water is circulated via a

steam drum. The gases are cleaned by washing and are discharged to the atmosphere by an exhaust fan.

Steam from the waste heat boilers is piped to a super-heater unit in an adjoining building and then distributed to

other plats.

STEEL CONVERTER:

NO OF CONVERTERS 2

TYPE TOP BLOWN OXYGEN CONVERTER 130T

WORKING VOLUME 93M3

SPECIFIC VOLUME M3/T 0.68

RATIO H/L 1.68

MOUTH DIA 2430mm

INNER HEIGHT 7125mm

INNER DIA 4240mm

Continuous casting machine: SLAB CASTER

NO OF MACHINES 2

NO OF STRANDS 02 (each)

THICKNESS 150-200mm

WIDTH 700-1550mm

TYPE OF MACHINE RADIAL CURVILINEAR

MACHNE RADIUS 10m

CASTING SPEED 0.6-0.9m/min

CAPACITY 825,000T/year

BLOOM CASTER

NO OF MACHINES 1

NO OF STRANDS 4

SIZE 200x200mm, 260x260mm

TYPE OF MACHINE RADIAL

MACHINE RADIUS 12m

CASTING SPEED 1.1-1.2m/min

CAPACITY 400,000T/year

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BILLET CASTER

NO OF MACHINES 1

NO OF STRANDS 6

CAPACITY 400,000T/year

SIZE 150x150 / 125x125 / 100x100 /

80x80

TYPE RADIAL

AVERAGE CASTING SPEED

150x150 1.5m/min

125x125 1.8m/min

100x100 2.5m/min

80x80 3-4m/min

METAL FLOW CONTROL IN MOULD

METERING NOZZLE

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THERMAL POWER PLANT AND TURBO BLOWER STATION (tpp-tbs) TPP stands for thermal power plant which is used for the generation of electricity for Pakistan Steel Mills.

TPP is broadly divided into following 5 sections:

Water chemical treatment plant (WCTP)

Boiler

Turbine

Generator

Main switch gear room (MSGR)

WATER CHEMICAL TREATMENT PLANT:

Before supplying water to boiler, it is chemically treated to remove impurities from raw water. Impurities present in

raw water are called total dissolve solid (TDS), which is broadly divided into three types:

Organic impurities

Inorganic impurities

Bio impurities

The main concern is with inorganic impurities (Ca, Mg) which cause hardness of water.

Hardness is of two types:

Temporary hardness

Permanent hardness

TEMPORARY HARDNESS:

Temporary hardness of water is caused by the presence

of dissolved bicarbonate minerals. When dissolved, these minerals yield

Calcium and magnesium cations (Ca2+, Mg2+)

Carbonate and bicarbonate anions (CO32-, HCO3

-).

To remove temporary hardness raw water is passed through:

Clarifiers

Line coagulated water storage

Mechanical filters

PERMANENT HARDNESS:

rmanentPe hardness of water is caused by the presence of dissolved sulfates and/or chlorides. When dissolved,

these minerals yield

Calcium and magnesium cations (Ca2+, Mg2+)

Sulfate and chloride anions (SO42-, Cl-).

Permanent hardness cannot be removed by boiling.

After removing temporary hardness, permanent hardness is removed from water by passing the water through:

Primary H-cation exchangers

Primary anion exchangers

Decarbonizers

Decarbonized water storage

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Secondary H-cation exchangers

Secondary anion exchangers

After passing through these stages, hardness is completely removed from water and demineralized water is

achieved.

Treated water output from water chemical treatment plant is 230 tons/hour.

BOILER:

The water from WCTP passes through different stages before reaching boiler:

Condensate pump

Low pressure heaters

Deriators

Boiler feed pump

High pressure heaters

After passing through these stages water reaches the four boilers in TPP, whose working pressure is 100kg/cm2 and

temperature of water is 215 oC.

BOILER PARTS:

Burner:

TPP consists of 4 burners, in which different fuels are burnt to convert water into steam

In 2 burners, natural gas and coal tar is burnt

In 2 burners, BF gas (obtained from blast furnace ) and coke oven gas is burnt

Boiler drum:

In boiler drum, the temperature of steam is 320oC, which is in saturated form; the steam is then passed through

super heaters, which increase the temperature of steam up to 540 oC.

IDF and FDF:

FDF (force draught fan) sucks air from environment and passes it to the burner for combustion of fuels producing

the flue gases (flue gas refers to the exhaust gas produced at power plants). Its composition depends on what is

being burned, but it usually consists of nitrogen(typically more than two-third) derived from the combustion

air, carbon dioxide (CO2), and water vapor as well as excess oxygen (also derived from the combustion air) are

passed through recirculating air heaters, release heat here and goes out in environment through IDF (induced

drought fan).

After passing through super heaters steam moves out of the boiler at 100kg/cm2, steam temperature 535 oC and

enters turbine.

TURBINE:

There are three turbines in TPP:

Turbine-1 is double cylinder type coupled with Generator 1

Turbine-2 and Turbine-3 are single cylinder type coupled with Generator 2 and Generator 3 respectively.

These turbines are impulse type and have 22 stages.

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TURBINE PARTS:

Stop valve is used for emergency tripping to stop the supply of steam to the generator.

Regulators are used to control the amount of steam supplied, i.e. depending on the demand of steam,

regulators are opened or closed.

Governor gives instruction to regulator valves to open or close and provide steam to serve load.

The servo motor is an amplifier which amplifies the order of the governor.

Bearing gear is used to initially move a rotor to remove distortion, it is switched on before turning the

turbine on.

Oil pump is used for pumping the oil.

Oil is used for lubrication of bearings and governor control.

The temperature of drain oil is 65 oC, the oil cooler drops the temperature of oil up to 40 oC.

MAIN PARAMETERS OF TURBINE

TURBINE TYPE ΠT-60-90/13

Two extraction = 10-16 ata & 1.5-3 ata

Rated out put = 60, 000 kW (60 MW)

Speed = 3, 000 rpm (50 Hz)

Live steam pressure after emergency stop value = 90 Kg/Cm2 (85-95)

Live steam temperature emergency stop valve (525 – 540) = 535°C

Frequency = (50 Hz)

Cooling water flow passing through condenser = 8000 m3/hr

Cooling water inlet temperature (28 - 33) = 28°C

Max. steam flow @ nominal conditions comprises respectively = 402 t/hr

Production extraction pressure = 13 ± 3 kg/cm2

District heating extraction pressure = 1.2 kg/cm2

Pressure control within = 0.7-2.5 Kg/cm2

Normal parameters of live steam, cooling water flow = 8000 m2/hr

Normal parameters of live steam cooling water flow Temp: = 28°C

The load up to = 75 MW

Pressure behind the overloading should not more than = 70 Kg /cm2

maximum steam flow to condenser = 170 t/hr

Oil temperature after oil cooler = 40°C

Oil temperature from Bearing drains not more than = 65°C

Bearing pressure = 1.01 - 1.03 Kg/cm2 (1.15 - 1.2 Kg/cm2)

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COMPRESSOR

Type = K-3250-42-1

Pressure = 3.5 Kgf/cm2 (Gauge Pressure)

Flow rate = 2100 M3/Minimum

Speed = 3250 rpm

Oxygen enrichment = 30%

Cooling = Seawater at 500 M3 /hour

Critical speed = 1600 rpm

Casing = Cast Iron

Diaphragms = Cast Iron

Rotor = Steel

Weight of Compressor = 77 Tones

Weight of heavier part = 23 T

Maximum allowable Pressure inside air Column = 3 Kgf/cm2

GENERATOR:

TPP has three turbo generators of 55 MW each coupled with steam turbines to serve the load of Pakistan Steel

Mills. Two of these generators are usually in working conditions while the third generator is kept in reserve.

Pakistan Steel Mills is also connected with KESC through two interconnected transformers which steps up the

voltage from 11kV to 132kV for transmission.

GENERATOR SPECIFICATIONS:

Rated voltage 11.5kV.

Speed 3000 rpm

Power factor 0.8

Stator current 3460A

Rotor current 1280 A

Hydrogen pressure 196 kPa.

Rated power 68750 kVA.

GENERATOR COOLING:

Hydrogen gas is used as a cooling medium in turbo generators.

The use of gaseous hydrogen as a coolant is based on its properties as follows

Low density,

High specific heat, and

Highest thermal conductivity (at 0.168 W/(m·K)) among all gases

Hydrogen gas is 7-10 times better at cooling than air.

Another advantage of hydrogen is its easy detection by hydrogen sensors. A hydrogen-cooled generator can be

significantly smaller, and therefore less expensive, than an air-cooled one.

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GENERATOR PROTECTION:

Generator protection is of two types,

Internal protection

External protection

INTERNAL PROTECTION:

Internal protections are of two types,

Longitudinal protection

Earth fault protection

Longitudinal protection:

Longitudinal protections are of two types,

Longitudinal differential

Cross protection EXTERNAL PROTECTION: External protection is for negative sequence and overcurrent faults.

MAIN SWITCH GEAR ROOM:

CONTROL ROOM:

The control circuit is controlled through DC supply so that the protective system remains unaffected in the absence

of AC supply from the generators.

DC BATTERIES:

There are 130 batteries of 2V each and current capacity of 1250 A/hr . 106 batteries are currently working while 24

batteries are in spare. These are lead acid batteries in which sulfuric acid is used as an electrolyte.

ADVANTAGES AND DISADVANTAGES OF THERMAL POWER PLANT:

ADVANTAGES:

Fuel is cheaper.

Smaller space is required as compared to hydro power plants.

Economical initial cost as compared to hydro power plants.

Can be placed near load centers, unlike hydro and nuclear power plants.

DISADVANTAGES:

Requires higher maintenance and operational cost.

Causes air pollution.

Requires the abundant amount of water.

Efficiency is less i.e. 30-35%.

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CONCLUSION

It was a great experience for me and I admit that I learnt a lot from Pakistan Steel Mill. All the staffs of all

departments were very cooperative and humble my interaction with people here has indeed helped me enhance

my communication skills and public relation skills. Things I learnt from here will not only help me in polishing my

studies, I have learnt so far, but also will benefit me in my practical life. As an engineer it was a great opportunity

for me and with the fun I learnt a lot from here.

Overall, this six weeks experience will remain etched in my memory and I do look forward to perhaps being a part

of Pakistan Steel Mill in the future.